Fate of Toxic Organic Compounds in Wastewater Treatment Plants

A pilot plant study was conducted to evaluate the fate and behavior of 22 toxic organic compounds (four pesticides, three phenols, six phthalates, and nine PAHs) in conventional wastewater treatment plants. Two parallel 0.1-L/s (1.5-gpm) treatment sequences were operated-a control, and an experimental sequence spiked with the 22 compounds being investigated. The organic compounds studied, spiked at a nominal concentration of 50 μg/L each, were typically removed to the 95 to 98% level. Many were partitioned to the primary and return activated sludges. Biodegradability was variable and was a function of molecular structure. Although the toxic compounds were generally well removed, effluent concentrations of several were high enough to be of environmental concern. These compounds were lindane, bis-(2-ethylhexyl)-phthalate, di-n-butylphthalate, and phenol.